Human rights groups are urging the Obama administration to halt an impending visit by the Chinese president to Washington amid reports that Beijing has launched a sweeping crackdown against dozens of rights lawyers in the country.

More than two-dozen human rights lawyers and activists have been detained by authorities or have disappeared since last week, a campaign of repression that analysts say is unprecedented. Another group of more than 100 lawyers and sympathizers were warned against agitating for their colleagues’ release and in some cases were briefly held by police.

The detention of lawyers follows China’s recent enactment of a new national security law, which critics say is a thinly veiled measure to curtail freedom of expression and criticism of the Communist Party. Activists say the law is now being used to crush an inchoate civil society in China that emerged when lawyers—who often do not accept compensation from their poor clients—encouraged citizens to stand up for their rights.

Beijing’s suppression of lawyers and civil society presents a challenge to President Obama, who has largely adopted the policies of previous administrations and pursued engagement with China's leaders. Xi Jinping, the Chinese president and party head who is viewed as the country’s most authoritarian and ideological leader since Mao Zedong, is slated to make his first state visit to Washington in September.

Analysts in the human rights community have called on Obama to suspend that meeting with Xi until the lawyers are released, though some suspect the visit will go forward as planned.